In a known power switchgear, a vacuum valve is configured by containing a fixed contact and a movable contact disposed with a predetermined distance spaced apart from the fixed contact in a vacuum vessel. The movable contact is coupled to a coupling rod of an electromagnetic operating mechanism via an insulating member and a contact pressure spring. The coupled vacuum valves and the electromagnetic operating mechanisms are disposed for three phases in parallel to each other with a predetermined distance spaced and are contained in a containing box.
Furthermore, a spring receiver is fixed at a lower end portion of the coupling rod and a coil shaped release spring serving as a spring member is put in a compressed state between a yoke of the electromagnetic operating mechanism and the spring receiver; and accordingly, spring force of a downward contact opening direction is applied to the coupling rod via the spring receiver during a contact opening operation so as to assist driving force during the contact opening.
In the structure of such known power switchgear, three units of the operating mechanisms are placed on one base plate; the vacuum valve, the contact pressure spring, the electromagnetic operating mechanism, and the release spring are coaxially arranged; and these coaxially arranged components are disposed for three phases in parallel to each other with a predetermined distance spaced and are contained in the containing box. This structure accelerates the contact opening speed of a movable element of the vacuum valve; and thus, electromagnetic force of the electromagnetic operating mechanism and force of the release spring are added. (See, for example, Patent Document 1.)
Furthermore, in other known power switchgear, vacuum valves and a release spring are coaxially arranged; the vacuum valves are disposed for three phases in parallel to each other with a predetermined distance spaced; and main circuit insulating frames insulate between respective phases. One driving shaft, which is disposed in a direction perpendicular to axial directions of the three phase vacuum valves and passes through movable shafts of the three phase vacuum valves, is provided and this one driving shaft pivots by an electromagnetic operating device coupled to the driving shaft; and accordingly, the respective movable shafts of the three phase vacuum valves are driven collectively, and opening and closing of fixed contacts and movable contacts of the three phase vacuum valves is performed collectively in three phases. (See, for example, Patent Document 2.)